rrcc/src/Assembler.h

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#pragma once


#include "Parser.h"
#include "instructions/Instruction.h"

class Assembler {
private:
    const Parser &parser;
    std::vector<uint8_t> bytes;
    std::unordered_map<std::string, uint32_t> knownRegisters;
    std::unordered_map<std::string, std::pair<uint32_t, bool>> entries;

    uint32_t placeFunction(uint32_t base, const Function &function) {
        std::unordered_map<std::string, uint32_t> addr;

        auto declarations = function.declarations; //Copy is necessary

        uint32_t offset = base;

        //Resolve local labels
        for (auto &d : declarations) {
            if (!d.label.empty()) {
                addr[d.label] = offset;
            }

            bool hasOperator = false;
            for (auto &t : d.tokens) {
                if (t.getType() == Token::Type::Operator) {
                    hasOperator = true;
                    break;
                }
            }

            if (!hasOperator) {
                continue;;
            }

            auto instr = Instruction::Instruction::getCommandForDeclaration(d);
            if (instr == nullptr) {
                throw std::runtime_error("Unknown or invalid declaration");
            }

            auto b = instr->toBytes();
            offset += b.size();
        }

        offset = base;

        bool needsReLabeling = false;

        for (auto &d : declarations) {
            for (auto &t : d.tokens) {
                if (t.getType() == Token::Type::CodeLabel) {
                    if (t.getTextValue().at(0) == '.') {
                        if (addr.find(t.getTextValue()) != addr.end()) {
                            t.valueImmediate = addr.at(t.getTextValue());
                        } else {
                            throw std::runtime_error("Could not find local label " + t.getTextValue());
                        }
                    } else if (entries.find(t.getTextValue()) != entries.end()) {
                        t.valueImmediate = entries.at(t.getTextValue()).first;
                    } else {
                        needsReLabeling = true;
                    }
                } else if (t.getType() == Token::Type::RegisterName) {
                    if (knownRegisters.find(t.getTextValue()) != knownRegisters.end()) {
                        t.valueImmediate = knownRegisters.at(t.getTextValue());
                    } else {
                        throw std::runtime_error("Could not find named register " + t.getTextValue());
                    }
                }
            }
        }

        for (auto &d : declarations) {
            auto instr = Instruction::Instruction::getCommandForDeclaration(d);
            if (instr == nullptr) {
                throw std::runtime_error("Unknown or invalid declaration");
            }

            if (!d.label.empty()) {
                addr[d.label] = offset;
            }

            auto data = instr->toBytes();

            if (offset + data.size() > +bytes.size()) {
                throw std::runtime_error("Instruction encoding exceeds image size");
            }

            std::copy(data.begin(), data.end(), bytes.begin() + offset);
            offset += data.size();
        }

        entries[function.label] = {base, needsReLabeling};

        return offset + 4; //Free bytes between functions
    }

    const Function *getFunctionByLabel(const std::string &l) {
        for (auto &f : parser.getTree()) {
            if (f.label == l) {
                return &f;
            }
        }

        return nullptr;
    }

public:

    Assembler(const Parser &parser) : parser(parser) {

    }

    //Default max size 1 MiB
    void assemble(uint32_t baseAddress = 0x08000, uint32_t imageSize = 0x100000) {
        entries.clear();
        bytes.clear();
        bytes.resize(imageSize - 1, (uint8_t) Instruction::Instruction::CommandOp::END);

        uint32_t freeOffsetLocation = baseAddress;

        auto entrypoint = getFunctionByLabel("entrypoint");
        if (entrypoint == nullptr) {
            throw std::runtime_error("Entrypoint function not found");
        }

        freeOffsetLocation = placeFunction(freeOffsetLocation, *entrypoint);

        while (true) {
            bool changed = false;
            for (auto &fEntry : entries) {
                if (fEntry.second.second) {
                    auto f = getFunctionByLabel(fEntry.first);
                    for (auto &d : f->declarations) {
                        for (auto &t : d.tokens) {
                            if (t.getType() == Token::Type::CodeLabel && t.getTextValue().at(0) != '.') {
                                if (entries.find(t.getTextValue()) == entries.end()) {
                                    changed = true;
                                    auto fUsed = getFunctionByLabel(t.getTextValue());
                                    if (fUsed == nullptr) {
                                        throw std::runtime_error(
                                                t.getTextValue() + " function not found, in use by " + fEntry.first);
                                    }

                                    freeOffsetLocation = placeFunction(freeOffsetLocation, *fUsed);
                                }
                            }
                        }
                    }

                    placeFunction(fEntry.second.first, *f);
                }
            }

            if (!changed) {
                break;
            }
        }

    }

    const auto &getImage() const {
        return bytes;
    }
};